System and/or method for heat treating conductive coatings using wavelength-tuned infrared radiation

ABSTRACT

Certain example embodiments relate to systems and/or methods for preferentially and selectively heat treating conductive coatings such as ITO using specifically tuned near infrared-short wave infrared (NIR-SWIR) radiation. In certain example embodiments, the coating is preferentially heated, thereby improving its properties while at the underlying substrate is kept at low temperatures. Such techniques are advantageous for applications on glass and/or other substrates, e.g., where elevated substrate temperatures can lead to stress changes that adversely effect downstream processing (such as, for example, cutting, grinding, etc.) and may sometimes even result in substrate breakage or deformation. Selective heating of the coating may in certain example embodiments be obtained by using IR emitters with peak outputs over spectral wavelengths where the conductive coating (or the conductive layer(s) in the conductive coating) is significantly absorbing but where the substrate has reduced or minimal absorption.

FIELD OF THE INVENTION

Certain example embodiments of this invention relate to systems and/ormethods for heat treating conductive coatings using wavelength-tunedinfrared (IR) radiation. More particularly, certain example embodimentsof this invention relate to systems and/or methods for preferentiallyand selectively heat treating conductive coatings such as indium tinoxide (ITO) using specifically tuned near infrared-short wave infrared(NIR-SWIR) radiation. In certain example embodiments, the coating willbe preferentially heated thereby improving its properties while at thesame time keeping the underlying substrate temperatures low.

BACKGROUND AND SUMMARY OF EXAMPLE EMBODIMENTS OF THE INVENTION

Transparent conductive oxide coatings, such as indium tin oxide (ITO),as well as other conductive (e.g., metallic) coatings deposited bymagnetron sputtering on unheated substrates are often thermally annealedto improve the functional properties of the material by improving itscrystallinity. In the case of ITO, for example, this is done primarilyto increase conductivity and to decrease absorption. It will beunderstood that the term “unheated substrates” are those to which noadditional thermal energy is intentionally provided during depositionand include, for example, so-called room temperature depositions. Bycontrast, however, it is understood that some rise in the temperature ofthe substrate will occur from physical vapor deposition (PVD) processessuch as sputtering.

For the case of coatings on glass and other temperature sensitivesubstrates, it is often not possible or practical to use radiative,conductive, or convective furnace heating processes commonly usedthroughout the glass industry for the tempering and/or heatstrengthening of glass. In the case of glass, for example, exposures toexcessively high temperatures (typically over 600 degrees C.) can leadto significant stress changes in the glass, sometimes even resulting infracture or deformation. And even at lower temperatures, significantstress changes may occur when exposure times are lengthy. These changesmay effectively render the glass unprocessable, e.g., to the point whereit can no longer be cut, ground, drilled, or otherwise fabricated intoits final physical form.

Conversely, stress changes in the glass are often exploited duringtempering and heat strengthening processes, e.g., to improve themechanical properties of the glass by placing the inner volume of thematerial under tension and the outer skin under compressive stress. Asis known by those skilled in the art, the cost of such processing can behigh and sometimes even greater than the cost of the glass itself.Additionally, the glass typically cannot be processed any furtherfollowing tempering or heat strengthening. Therefore, tempering and heatstrengthening processes are typically employed only where required forproduct functionality and/or safety.

The assignee of the instant application is currently developing a numberof products that utilize ITO as a transparent conductive layer. Suchproducts are being developed for use in anticondensation and otherapplications, e.g., where such low emissivity products are used inresidential and/or other applications. When the glass is mountedvertically in these applications, as in the case of a typical window, itis usually not tempered or heat strengthened. Approximately 75-80% ofthe market by volume falls under this category. Therefore, windowmanufacturers often are not setup to handle high volume tempering and/ordo not wish to bear the additional costs and logistics associated withusing tempered glass. Thus, it will be appreciated that delivering anannealed “stock sheet” solution that customers can fabricate intowhatever final form they desire would be advantageous to the marketadoption of these products. It also will be appreciated that thetechniques described herein may be advantageous in other applicationswhere transparent conductive oxide materials are used such as, forexample, displays and touch screen products.

In general, it will be appreciated that it would be desirable to provideimproved techniques for heat treating coatings in a way that has areduced impact on the underlying substrate.

Certain example embodiments of this invention relate to a method ofmaking a coated article. A glass substrate is provided. A layer ofindium tin oxide is formed, directly or indirectly, on the substrate viaphysical vapor deposition. The glass substrate with the layer of indiumtin oxide thereon is exposed to infrared radiation at a peak emission of1-2 μm for up to about 108 seconds so as to cause the sheet resistance,emissivity, and absorption to be lower than corresponding values for theas-deposited layer of indium tin oxide. The layer of indium tin oxide ispreferentially heated such that the glass substrate does not reach atemperature in excess of about 480 degrees C.

Certain example embodiments of this invention relate to a method ofmaking a coated article. A Glass substrate with a layer of indium tinoxide sputter deposited thereon is provided. The glass substrate withthe layer of indium tin oxide thereon is exposed to infrared radiationat a peak emission of 1-2 μm for a time sufficient to cause the sheetresistance, emissivity, and absorption to be lower than correspondingvalues for the as-deposited layer of indium tin oxide, with the sheetresistance following the exposure to the infrared radiation beingsubstantially the same as the sheet resistance would be if the coatedarticle were heated in a conventional radiant furnace for 3.5 min at 650degrees C. The layer of indium tin oxide is preferentially heated suchthat the glass substrate does not reach a temperature in excess of about425 degrees C.

Certain example embodiments of this invention relate to an infrared heattreatment system configured to heat treat a coated article comprising aglass substrate having a coating physical vapor deposition depositedthereon. An infrared heating element is configured to irradiate infraredradiation at a peak emission of 1-2 μm at the coated article for apredetermined amount of time so as to cause preferential heating of thecoating or a portion of the coating such that the glass substrateremains at a temperature below 480 degrees C. without any additionalcooling elements. The coating comprises at least one layer of indium tinoxide.

The features, aspects, advantages, and example embodiments describedherein may be combined to realize yet further embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages may be better and morecompletely understood by reference to the following detailed descriptionof exemplary illustrative embodiments in conjunction with the drawings,of which:

FIG. 1 is a schematic view of a system incorporating an IR heater inaccordance with certain example embodiments;

FIG. 2 is an example coating upon which the IR techniques of certainexample embodiments were used;

FIG. 3 plots percent transmission, reflection, and absorption againstwavelength for a coated sample produced in accordance with an exampleembodiment;

FIG. 4 plots percent transmission, reflection, and absorption againstwavelength for an uncoated glass substrate;

FIG. 5 plots sheet resistance and percent absorption as a function ofheating time for certain example embodiments;

FIG. 6 plots substrate temperature as a function of heating time forcertain example embodiments;

FIG. 7 plots power density vs. IR heat treatment time requirements,e.g., to reach a sheet resistance of 20 ohms/square; and

FIG. 8 plots sheet resistance and absorption as a function of time fortimes and temperatures.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

Certain example embodiments relate to techniques for the post-depositionheat treatment of indium tin oxide (ITO) coatings on glass substratesusing high-intensity, wavelength-tuned infrared (1R) radiation. The useof particular wavelengths of NIR-SWIR radiation advantageously enablesselective heating of the ITO layer while a relatively low substratetemperature is maintained. Additionally, processing times may be reducedover conventional means. This is particularly advantageous forapplications on glass and/or other substrates, e.g., where elevatedsubstrate temperatures can lead to stress changes that adversely effectdownstream processing (such as, for example, cutting, grinding, etc.)and may sometimes even result in substrate breakage or deformation.Selective heating of the coating may in certain example embodiments beobtained by using IR emitters with peak outputs over spectralwavelengths where ITO is significantly absorbing but where the substrate(e.g., glass) has reduced or minimal absorption. This technique may alsobe applicable for other transparent conductive coatings including, forexample, others types of transparent conductive oxides (TCOs), othermetallic (e.g., silver) films, etc.

By preferentially heating the coating using the high-intensity,wavelength-tuned IR radiation techniques described herein, heattreatment of the ITO layer is possible at lower substrate temperaturesand/or shorter heating times than would be required by conventionalmeans. Preferential heating is achieved by using IR wavelengths that areabsorbed much more strongly by the coating than the substrate. Highintensity IR radiation may be supplied, for example, by quartz lamps orlaser emitters.

In the case of laser emitters, laser diode arrays may be advantageous,e.g., given their lower cost of ownership compared to other common lasertypes (and the availability of 940 nm wavelength output matches wellwith the spectral characteristics of the coating). However, excimer,CO₂, YAG, quartz, and/or other types of lasers and/or lamps also may beused in different embodiments. In certain example embodiments,electromagnetic radiation may be focused into a very high aspect ratiorectangular beam spanning the width of the glass. The glass may betraveling on a conveyor in a direction perpendicular to the long axis ofthe rectangle. In certain example embodiments, a “step and repeat”process may be employed, e.g., so as to irradiate smaller sections in acontrolled manner such that the entire substrate ultimately isirradiated. In addition, other sizes and/or shapes may be usedincluding, for example, substantially square shapes, circular shapes,etc.

In general, higher power densities have been found to be preferablebecause they permit shorter heating times and higher temperaturegradients from the coating through the bulk substrate. With shorterheating times, less heat is transferred from the coating through theglass via conduction and a lower temperature may be maintained.

Advantages of the example approaches described herein may include, forinstance, increased coating conductivity, reduced coating emissivity,reduced coating absorption, etc. Another advantage of the exampleapproaches described herein may come from the ability to provide suchtreatments to temperature-sensitive substrates.

FIG. 1 is a schematic view of a system incorporating an IR heater inaccordance with certain example embodiments. The FIG. 1 example systemincludes a coater 102 for physical vapor depositing one or more thinfilm layers on a substrate, e.g., via sputtering. Downstream of thecoater 102 is an IR heater 104. In certain example embodiments, a roomtemperature sputtering apparatus may be used to deposit ITO on a glasssubstrate. A conveyor system 106 conveys a substrate through the coater102, where the layer or layer stack is deposited, and to the IR heater104. The IR heater 104, in turn, is tuned to focus NIR-SWIR radiation atthe substrate with the coating thereon. The wavelength of the IRradiation is selected to as to preferentially heat the coating or aparticular layer in the coating, e.g., as compared to the substrateand/or any other layers in a multilayer coating.

Although certain example embodiments have been described as including anIR heater downstream of the coater, it will be appreciated thatdifferent example embodiments may locate a coater within a vacuumchamber of the coater. In addition, in certain example embodiments, theIR heat treatment may be performed at any time once the layer to be heattreated or activated has been deposited. For instance, certain exampleembodiments may perform an IR heat treatment just after ITO layerdeposition, whereas certain example embodiments may perform an IR heattreatment once all layers in a layer stack have been deposited. Incertain example embodiments, multiple IR heat treatments may beperformed at different times during the deposition process.

Example

A test was performed using a short-wave infrared (SWIR) furnaceincorporating quartz lamps. A peak IR emission wavelength of 1.15 μm wasused to heat the coating. This wavelength was determined by analyzingthe spectral characteristics of the coating and the glass substrate. Thepower density of the SWIR furnace is 10.56 kW/ft² (bulb output is 80W/in, with mounting on 1″ centers). Heating times ranged from 12-130 secwith 12 sec intervals. Heating elements were about 4″ from the glasssurface, although the heating elements may be raised or lowered indifferent example embodiments of this invention.

FIG. 2 is an example coating upon which the IR techniques of certainexample embodiments were used. FIG. 2 includes a glass substrate 201supporting a multilayer coating. The multilayer coating comprises an ITOlayer 205 sandwiched by two silicon-inclusive layers. The ITO layer 205in the FIG. 2 example embodiment is 120 nm thick. A first layer 203comprising SiO_(x)N_(y) layer is interposed between the glass substrate201 and the ITO layer 205, and is 67 nm thick. A second layer 207comprising SiN is provided, directly or indirectly, on the ITO layer205. An optional zirconium oxide layer 209 is provided as a top-mostlayer, e.g., for durability purposes. The glass substrate was 3 mm clearfloat glass.

Measured spectral data for the coated sample and uncoated glasssubstrate are presented in FIGS. 3 and 4, respectively. Moreparticularly, FIGS. 3 and 4 plot percent transmission, reflection, andabsorption against wavelength for the coated sample and uncoated glasssubstrate, respectively. FIG. 3 shows the absorption of the glasssubstrate to be relatively low over the IR spectral range of 0.8-2.5 μm.Low absorption in the glass is desirable to reduce the amount of directheat transfer to the glass by radiation.

The reflectivity of the ITO containing coating stack has a minimumaround 1.1 μm. Reflectivity increases rapidly at increasing wavelengths,leading to a reduction in efficiency of the heating process. Atwavelengths longer than 2 μm, the majority of the incoming radiation isreflected by the coated surface.

From these observations, an appropriate wavelength range for heating of0.8-2.5 μm has been established. More preferably, the IR emission rangeis 1-2 μm. The above-described techniques may be used to establishoptimum or preferred IR emission ranges for heat treating other coatings(e.g., other TCO, metallic, etc. coating) on glass, as well.

By targeting IR wavelengths absorbed by the coating, it is possible togenerate a large thermal gradient between the coating and bulksubstrate. Because the thermal mass of the coating is very smallcompared to the glass, the glass essentially acts as a quench mechanism.The rise in bulk glass temperature is mainly attributed to direct heattransfer by IR absorption, rather than by conduction from the coating.

FIG. 5 plots the results of the above test. After only 80 sec ofheating, the sheet resistance decreased by 70%. After 108 sec, sheetresistance is comparable to samples heated in a conventional radiantfurnace for 3.5 min. at 650 degrees C. However, absorption is higher,likely indicating a lower oxidation state compared to the temperedbaseline.

After only 48-60 sec of heating, the final crystallinity of the film isobtained. No significant differences in grain size or lattice strainwere observed with additional heating.

Substrate temperature is plotted in FIG. 6 as a function of heatingtime. Sheet resistance is also plotted for reference. The substratetemperature only reaches 210 degrees C. after 60 sec of heating. Itapproaches 360 degrees C. after 108 sec of heating when the coatingproperties become comparable to those of a tempered sample. Thesubstrate temperature is around 300 degrees C. lower in this case.

The initial oxidation level of the ITO on the samples used herein hasbeen optimized for low sheet resistance following tempering (whichresults in additional oxidation of the ITO). It is likely that adifferent optimum exists for heat treating ITO using NIR radiation. Whenthe initial oxidation level of the ITO is optimized for NIR heating, itshould be possible to significantly reduce the amount of heatingrequired. Theoretically, this time should be reduced to the 48-60 secrequired for re-crystallization using the same heating process. Furtherdecreases is heating time may be achieved by optimizing the powerdensity vs. heating time requirements.

FIG. 7 plots power density vs. IR heat treatment time requirements,e.g., to reach a sheet resistance of 20 ohms/square. Interestingly, inthe FIG. 7 graph, the glass temperature was found to be near 400 degreesC., regardless of power density.

Although a certain ITO-based layer stack has been described above, itwill be appreciated that the techniques described herein may be used inconnection with other ITO-based layer stacks. For instance, thetechniques may be applied to a coated article having a coating formedthereon, with the coating comprising an optional first silicon-inclusivelayer ranging from about 30-100 nm in thickness (e.g., SiO_(x), SiN,SiO_(x)N_(y), etc.), a layer of ITO ranging from about 70-200 nm inthickness (more preferably about 115 nm in thickness), and a secondlayer silicon-inclusive layer ranging from about 30-100 nm in thickness(e.g., SiO_(x), SiN, SiO_(x)N_(y), etc.). One or more optional topcoats(e.g., of or including one or more of zirconium oxide, zirconiumnitride, aluminum oxide, aluminum nitride, DLC, or the like) also may beprovided to improve durability, provide hydrophilic or hydrophilic-likeand/or photocatalytic properties (e.g., one or more of anatase TiO₂,BiO, BiZr, BiSn, SnO, or the like), etc.

Furthermore, other ITO-based layer stacks also may benefit from the IRheat treatment techniques described herein. See, for example, theembodiments disclosed in application Ser. Nos. 12/662,894 and12/659,196, the entire contents of which are each hereby incorporated byreference. As one example, the following anticondensation coating maybenefit from the IR heat treatment techniques disclosed herein:

Example Thickness Example Range Thickness (nm) (nm) ZrOx  2-15 7 SiNx10-50 30 ITO  75-175 130 SiOxNy 10-50 35 TiOx  2-10 3.5 SiNx 10-20 13In the above example, ZrOx is the topmost layer, and SiNx is the layerclosest the glass substrate.

As indicated above, other TCOs may be used in place of, or in additionto, ITO. For instance, certain example embodiments may incorporate anITO/Ag/ITO sandwich. Certain example embodiments may incorporate zincoxide, aluminum-doped zinc oxide (AZO), p-type aluminum oxide, doped orun-doped Ag, FTO, and/or the like. When Ag is incorporated into thelayer stack system as a TCO, layers comprising Ni and/or Cr may beprovided directly adjacent (contacting) the Ag. In certain exampleembodiments, each layer in the layer stack system may besputter-deposited. Also as indicated above, other metallic thin filmcoatings may take advantage of the techniques described herein.

The NIR heating techniques described herein, furnace heating (attemperatures below the glass transition temperature), and flametreatment (e.g., according to the techniques disclosed in U.S.Publication No. 2008/0008829, the entire contents of which areincorporated herein) were studied, and the results of those techniqueswere compared to tempered baseline and untreated coatings. Although theoptical properties obtained from the various heat treatment methods aredifferent for coatings of similar crystallinity and sheet resistance,this is believed to be caused by a difference in the oxidation of theITO layer. The table below summarizes these results:

A Strain Grain Rs e Tvis a* b* Rf a* b* (calc) (×10⁻³) size (nm)Unheated - 63 .43 72.96 3.58 0.08 19.43 −12.14 10.83 7.61 1.8 19.3 asdeposited Baseline 20 .22 80.81 2.36 0.15 17.01 −8.94 0.09 2.18 2.5 13.7(650° C., 3.5 min) Box (300° C., 15 min) 23 .23 78.06 1.12 −1.54 17.12−5.78 6.57 4.82 2.4 14.2 Box (400° C., 9 min) 19 .23 79.14 1.58 −0.0417.18 −6.69 0.73 3.68 2.6 13.4 Flame Treatment 29 .28 77.09 1.17 −2.3917.68 −6.23 10.99 5.23 2.4 14.2 NIR (1.8 min) 19 .20 79.00 1.15 −1.2517.30 −5.93 4.22 3.70 2.5 13.9

As can be seen from the table above, the NIR heating techniquesdescribed herein provided the best results in terms of coatingproperties and the amount of time required for heat treatment.Re-crystallization to a structure comparable to the tempered samples wasfound to occur with only 48-60 sec. of heating, producing a substratetemperature near 200° C.

Flame treatment was found to cause significant re-crystallization withonly two burner passes. However, further improvements were not realizedwith additional passes under the burner, and the crystalline propertiesdid not quite match those obtained by tempering or NIR heating. It maybe possible to achieve similar results with an increase in flametemperature (e.g., acetylene flame) or heat flux (higher combustion gasthroughput). However, glass breakage remains a concern with flameheating because the thermal energy is applied very rapidly and only overa small area of the glass, leading to a large temperature gradientacross the glass surface in the direction of travel.

Furnace annealing was found to require much longer exposure timescompared to tempering. See, for example, FIG. 8, which shows how thecoating changes with furnace annealing at different temperatures andtimes. More particularly, FIG. 8 plots sheet resistance and absorptionas a function of time for times and temperatures. The added costsassociated with raising and lowering the furnace temperature along withthe long heating times required would lead to significantly higherthermal processing costs than could be achieved by standard tempering.Heat transfer is uniform, and does not specifically target the coating.The data obtained nonetheless provides a useful basis for comparison toother techniques.

The techniques described herein preferably preferentially heat the ITOin the coating such that the glass substrate remains below itstransition temperature, which is about 480 degrees C. for float glass.Preferably, the glass substrate remains below 450 degrees C., and morepreferably below 425 degrees C. In certain example embodiments, where apeak emission of 1.15 μm is applied for 108 sec, the sheet resistance ofthe example coating is about one-third of its as-deposited equivalent,and the emissivity and absorption correspondingly drop to about one-halfof their as-deposited counterpart values. In the meantime, the substratetemperature reaches a maximum of only about 400 degrees C., which iswell below its transition temperature.

NIR generally includes IR having a wavelength of 0.75-1.4 μm, and SWIRgenerally includes IR having a wavelength of 1.4-3 μm. Certain exampleembodiments may generally operate within these wavelengths. Thesubstrate temperature preferably does not exceed 480 degrees C., morepreferably 450 degrees C., still more preferably 425 degrees C., andsometimes 400 degrees C., as a result of such NIR-SWIR heating.

In certain example embodiments, following heat treatment or activationvia the techniques described herein, a coated article may be forwardedto a fabricator or other location, e.g., for further processing such as,for example, cutting, sizing, incorporation into a further article(e.g., a insulating glass unit, skylight, vehicle, glazing, etc.).Preferably, breaking or catastrophic failures of the heat treated coatedarticle will not result as a result of changes to the glass caused bythe heat treatment process.

As used herein, the terms “on,” “supported by,” and the like should notbe interpreted to mean that two elements are directly adjacent to oneanother unless explicitly stated. In other words, a first layer may besaid to be “on” or “supported by” a second layer, even if there are oneor more layers therebetween.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. A method of making a coated article, the methodcomprising: providing a glass substrate; forming a layer of indium tinoxide, directly or indirectly, on the substrate via physical vapordeposition; exposing the glass substrate with the layer of indium tinoxide thereon to infrared radiation at a peak emission of 1-2 μm for upto about 108 seconds so as to cause the sheet resistance, emissivity,and absorption to be lower than corresponding values for theas-deposited layer of indium tin oxide; and wherein the layer of indiumtin oxide is preferentially heated such that the glass substrate doesnot reach a temperature in excess of about 480 degrees C.
 2. The methodof claim 1, wherein the layer of indium tin oxide is formed bysputtering.
 3. The method of claim 2, wherein the sputtering is roomtemperature sputtering.
 4. The method of claim 2, wherein the exposureto the near infrared radiation is performed in a vacuum chamber.
 5. Themethod of claim 1, wherein the exposure to the near infrared radiationis performed downstream of a coater used to form the layer of indium tinoxide on the substrate.
 6. The method of claim 1, further comprisingdisposing a first silicon-inclusive layer, directly or indirectly, onthe layer of indium tin oxide prior to the exposure to the near infraredradiation.
 7. The method of claim 6, further comprising disposing asecond silicon-inclusive layer, directly or indirectly, on the substratesuch that the second silicon-inclusive layer is located between thesubstrate and the layer of indium tin oxide.
 8. The method of claim 7,wherein the first silicon-inclusive layer is SiO_(x)N_(y) and the secondsilicon-inclusive layer is SiN.
 9. The method of claim 8, furthercomprising disposing a ZrOx layer, directly or indirectly, on the firstsilicon-inclusive layer prior to the exposure to the near infraredradiation.
 10. The method of claim 9, wherein the peak emission is 1.15μm.
 11. The method of claim 9, wherein the sheet resistance of thecoating or the layer of indium tin oxide following the exposure to thenear infrared radiation is substantially the same as the sheetresistance would be if the coated article were heated in a conventionalradiant furnace for 3.5 min. at 650 degrees C.
 12. The method of claim9, wherein following the exposure to the near infrared radiation, thesheet resistance is reduced by one-third and the emissivity andabsorption are reduced by one-half.
 13. The method of claim 1, furthercomprising: disposing between the layer of indium tin oxide and theglass substrate layers comprising a layer of TiO_(x) sandwiched by firstand second silicon-inclusive layers; disposing, directly or indirectly,on the layer of indium tin oxide, a third silicon-inclusive layer; anddisposing, directly or indirectly, on the third silicon-inclusive layer,a ZrOx layer, wherein all layers are disposed on the substrate prior tothe exposure to the near infrared radiation.
 14. The method of claim 13,wherein the first and third silicon-inclusive layers comprise SiN_(x)and the second silicon-inclusive layer comprises SiO_(x)N_(y).
 15. Amethod of making a coated article, the method comprising: providing aglass substrate with a layer of indium tin oxide sputter depositedthereon; exposing the glass substrate with the layer of indium tin oxidethereon to infrared radiation at a peak emission of 1-2 μm for a timesufficient to cause the sheet resistance, emissivity, and absorption tobe lower than corresponding values for the as-deposited layer of indiumtin oxide, the sheet resistance following the exposure to the infraredradiation being substantially the same as the sheet resistance would beif the coated article were heated in a conventional radiant furnace for3.5 min at 650 degrees C.; and wherein the layer of indium tin oxide ispreferentially heated such that the glass substrate does not reach atemperature in excess of about 425 degrees C.
 16. The method of claim15, wherein the power density involved in the exposure to the infraredradiation is 10.56 kW/ft² to support a heating cycle time of 108 sec.17. An infrared heat treatment system configured to heat treat a coatedarticle comprising a glass substrate having a coating physical vapordeposition deposited thereon, the system comprising: an infrared heatingelement configured to irradiate infrared radiation at a peak emission of1-2 μm at the coated article for a predetermined amount of time so as tocause preferential heating of the coating or a portion of the coatingsuch that the glass substrate remains at a temperature below 425 degreesC. without any additional cooling elements, wherein the coatingcomprises at least one layer of indium tin oxide.
 18. The system ofclaim 17, wherein the infrared heating element is configured to operateat a power density of 10.56 kW/ft².
 19. The system of claim 18, whereinthe infrared heating element comprises a furnace incorporating quartzlamps.
 20. The system of claim 19, wherein the lamps have a bulb outputof 80 W/in, with mounting on 1″ centers.
 21. The system of claim 18,wherein the infrared heating element is located about 4″ from a surfaceof glass substrate.
 22. The system of claim 17, wherein the infraredheating element comprises a laser emitter.
 23. The system of claim 17,wherein the infrared heating element comprises a laser diode array. 24.The system of claim 17, wherein the infrared heating element isconfigured to produce electromagnetic radiation focusable into a veryhigh aspect ratio rectangular beam spanning a width of the glasssubstrate.